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CVE-2026-102273 high CVSS 7.4

Vulnerability in PyJWT (CVE-2026-102273)

Summary

Vulnerability in PyJWT (CVE-2026-102273). Confidential information can be exposed externally. Exploitable via kty. Mitigation: upgrade to 2.14.0 or later.

Original description

The description as published by the source.

Summary

PyJWT 2.13.0 contains an incomplete defense against algorithm confusion when
an application mixes symmetric and asymmetric algorithms in one verification
path. A public RSA, EC, or OKP JWK can be accepted as an HMAC secret when it
is wrapped in a JWKS object, nested in an array, or represented in another
container form that does not expose a top-level kty member.

Impact

An attacker who knows the public key material can forge HS256/HS384/HS512
tokens if the application simultaneously:

  • allows both HS* and asymmetric algorithms;
  • passes raw public JWK/JWKS JSON as key=; and
  • uses that same value as the HMAC secret.

This can allow forged JWT claims in affected application configurations. The
issue does not affect applications that keep symmetric and asymmetric
verification paths separate and follow PyJWT's algorithm-selection guidance.

Fix status

The fix is on master in commit 801cd12 (fix: reject public JWK container HMAC keys). HMACAlgorithm.prepare_key now rejects public JWK members found in
objects, arrays, nested containers, BOM/UTF variants, and recursion-limit
inputs. It also recognizes escaped JSON member names without treating ordinary
string values as JWKs. Ordinary JSON secrets remain accepted byte-for-byte.

The change was tested with focused regression tests and the full local tox
matrix. Available Python 3.9, 3.12, and 3.13 crypto/no-crypto suites, mypy,
package metadata, and coverage passed; unavailable interpreters were s…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-102273 has been found in PyJWT.
Attackers can target a specific entry point like kty over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade PyJWT to 2.14.0 or later.
If unsure, ask your IT team or search "PyJWT CVE-2026-102273" on the vendor's site.

CVE-2026-102273 (PyJWT) — CWE-347 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: kty / master / HMACAlgorithm.prepare_key
Patched: 2.14.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-347) exists in PyJWT. Attackers reach the vulnerable code path via kty without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of PyJWT. Attack surface: kty / master / HMACAlgorithm.prepare_key.

🔥 Severity

Severity: High (CVSS 7.4/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 2.14.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'PyJWT' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'PyJWT' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で PyJWT を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade PyJWT to 2.14.0

    ステージング環境で 2.14.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip PyJWT
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.14.0"}]}]

References

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